Slang is a self-sufficient, subversive, oppositional subset of the English language. It has given a tongue, by no means inarticulate, to the marginal, the criminal and the dispossessed for at least half a millennium. But it is hard to pin down: even the etymology of the word 'slang' remains unsubstantiated. Perhaps inevitably it challenges concrete linguistic definition, remaining a source of argument: is it a full scale language or simply a lexis of synonymy. And what exactly constitutes a 'slang' word, what qualifies it for inclusion in that lexis? Whatever the 'truth' it remains a flourishing and endlessly self-inventive channel of communication. As a slang lexicographer of thirty years' experience,